A few years ago, I was introduced to the use of TENs units. I had some elbow pain and my massage therapist offered to try transcutaneous electrical nerve stimulation (TENS). Sure enough, the pain subsided and after two treatments I was painfree. At some point, knowing that I am a sex therapist, she mentioned that various people were using these TENS units to bolster their sexual experience.
Intrigued, I began researching and discovered that there were several manufacturers of "Electro-simulation" units designed more specifically for sexual stimulation. While similar to TENS, there are significant differences. More and varied pulsing, levels of excitation, some even follow voice commands. While TENS units almost always use electrode pads of one sort or another, Electro-stim units also use specially contructed dildos, penile clamps, and "butt plugs," as well as the more common square adhesive electrodes. The variety seems limited only by the creativity of users and designers.
I discovered that there were three or four major manufacturers as well as a host of also-rans, most of whom merely repurposed TENS units by relabeling them. Two companies actually provided me with complete kits so I could test them, write a review and publish. Those two, ElectraStim from England, Erostek from California, would have been accompanied by a third, PES, now from Las Vegas, however PES was in managerial transition or so I was told and my request for information did not get a response.
The result was amazing. I recruited both male and female testers and we put those two systems through their paces. You can read the results on Joan Price's blog with a somewhat longer report here.
Since then Electrastim has supplied me with more attachments and products as well as their much upgraded Sensavox and I've published reviews in several venues as well as presenting E-stim to professional sexologists and sex therapists.